半滑舌鳎溃疡病原杀鲑气单胞菌的分离鉴定与药敏试验

Isolation and identification & antimicrobial susceptibility test of Aeromonas salmonicida associated with the skin ulceration disease of Cynoglossus semilaevis Günther

半滑舌鳎(Cynoglossus semilaevis Günther)是广受我国消费者认可的名优鱼类,具有很高的营养价值和经济价值,然而,随着工厂化养殖模式的不断发展,疾病成为制约半滑舌鳎养殖业健康发展的关键因素,其中,体表溃疡病为其常见病症。从严重溃疡病半滑舌鳎体内分离到1株优势菌株HX0416,该菌可在TCBS培养基上生长,并可在绵羊血平板上形成清晰的β-溶血环;经过16S rRNA和rpo D基因序列同源性分析并结合生化特性鉴定为杀鲑气单胞菌(Aeromonas salmonicida)。健康半滑舌鳎幼鱼感染试验表明,该菌对半滑舌鳎具有较强致病性,感染72 h(1.04×106cfu·m L-1)对攻毒鱼的致死率达91.7%。药敏试验结果显示,该菌对环丙沙星、恩诺沙星、诺氟沙星等喹诺酮类和头孢曲松、头孢吡肟等头孢菌素类药物比较敏感,而对硫酸新霉素、土霉素等氨基糖苷类和四环素类药物多重耐药,尤其是对磺胺甲噁唑、氨苄西林等磺胺类和β-内酰胺类药物严重耐药。

Cynoglossus semilaevis Gtinther is known as a famous fish in China for its high nutritional and economic value. However, with the continuous development of factory farming model, diseases have become the key factor to restrict the healthy development of Cynoglossus semilaevis GUnther aquaculture, and skin ulceration disease was the most common one. In this study, one dominant strain HX0416 was isolated from Cynoglossus semilaevis Gunther with severe skin ulceration disease. The bacterium could grow well on the TCBS agar and form the obvious beta hemolytic ring on the sheep blood agar. Analysis of 16S rRNA and rpoD gene sequence combined with biochemical characteristics demonstrated that the isolate HX0416 was Aeromorras salmonicida. Animal infection experiment showed that the strain was pathogenic to Cynoglossus semilaevis Gtinther. When the concentration of bacterium was 1.04 × 10^6 cfu/mL, about 91.7% juvenile fishes died at 72 h after infection. Antimicrobial susceptibility tests indicated that strain HX0416 was sensitive to quinolones and cephalosporins such as ciprofloxacin, enrofloxacin, norfloxacin, ceftriaxone and cefepime, while resistant to aminoglycosides and tetracyclines such as neomycin sulfate and oxytetracycline, and severely resistant to both sulfonamides and β-lactams such as sulfamethoxazole and ampicillin.